


boys will be boys

by bluebluewater



Category: Undertale (Video Game)
Genre: Gaslighting, Grooming, M/M, Parent/Child Incest, Sibling Incest, Suicidal Thoughts, Underage Rape/Non-con, Underage Sex, if there needs to be additional warnings for chapters i will warn in the notes, it doesn't really get worse than this though, nasty stuff y'know?
Language: English
Status: In-Progress
Published: 2021-01-15
Updated: 2021-02-01
Packaged: 2021-03-17 15:26:57
Rating: Explicit
Warnings: Rape/Non-Con, Underage
Chapters: 2
Words: 10,212
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28727316
Author URL: https://archiveofourown.org/users/bluebluewater/pseuds/bluebluewater
Summary: a present for @beetleevil on twitter. their art gives me life (and devious ideas >w> ) based off of their shotacon/lolicon art!Chapters 1-3 will be a continuation of each other.Ch 1. sans has always been a very smart child. Gaster just wants to further his education, no ulterior motive whatsoever!Ch 2. Not one to forget things, Papyrus is insistent sans share his present with him. With Gaster by his side, sans begrudgingly complies.Ch 3. Papyrus had been waiting for this day for a long time! Finally, he's ready to leave behind his stripes and enter the world of adult pleasures for good.Ch 4. His brother has always been pretty. sans' infatuation may have gone too far.Ch 5. Being the youngest child has it's perks, like having your loving older brother wrapped around your finger, for example. An older brother who could never say no to you. A brother who you were very curious about.
Relationships: Papyrus/Sans (Undertale), W. D. Gaster/Papyrus, W. D. Gaster/Papyrus/Sans, W. D. Gaster/Sans
Comments: 10
Kudos: 29





	1. Chapter 1

Gaster smiled pleasantly at his oldest son as he tried to show Papyrus how his new telescope worked. This was probably the most excited he’s ever seen sans - he knew it would be the telescope that did him in. Even if the real stars weren’t available to them sans still liked to look at the high ceilings of Waterfall and pick out his own constellations. He was always scribbling down new ones in the journal he kept with him, showing them to anyone who would listen. Gaster wouldn’t be surprised if sans published his own book of constellations one day. 

The day was winding down as his sons finished off the birthday cake their aunt had made. None of the skeletons could cook or bake to save their lives so having Myla do it was a good alternative. She had left about an hour ago and even Papyrus was starting to lag, it being almost his bedtime. Despite not wanting to sleep he was a stickler for schedules. 

Finally, after stifling his 6th yawn, sans got up and plodded over to Gaster, throwing his arms around his neck. “thanks, dad,” he mumbled sleepily. “that was a great present.”

“Ready for bed so soon?” Gaster teased, hoisting sans up into his lap. sans leaned back curiously when he continued. “I haven’t even given you the special present yet!” 

“wait, the telescope wasn’t the special present?” He had been hinting at it for weeks, and now the new teen was now wide awake, hanging onto his every word, as was Papyrus. 

“Ha, no of course not.” Gaster smiled smugly and sans frowned when no followup came. 

“what is it?” 

“Well, it’s just for you so we have to wait until your brother is asleep,” Gaster whispered next to his skull then chuckled when Papyrus heard anyway and started protesting. 

“I want to see what it is!” The nine year old dropped the interesting gadgets he had pilfered from the present pile and ran over to their dad. “Why can’t I see it?!” 

“It’s a special teenager present,” Gaster tilted his head, winking secretively at sans. “When you turn thirteen you’ll also get the present. You don’t want to spoil the surprise, surely.”

“I do! I hate surprises!” Papyrus insisted. He loved surprises. “Show me, pleeeeease?” 

“no, bro,” sans interjected, seeming annoyed that this was taking so long. “it’s just for me! if you go to bed now i’ll read you two books later, okay?”

He debated it for a moment, then chirped “Okay! But you have to tell me what it is later, okay?!”

“ok, pap,” sans easily agreed to their terms and conditions, twining their pinky fingers together before Papyrus raced to bed. 

“I give it five minutes until he’s out cold,” Gaster remarked as sans huffed a small laugh. 

“that’s the only reason i offered him two stories, cause i don’t have to do it. i’m really tired,” a statement he proved by yawning directly after. Then he stole a glance at his dad’s expression. “not too tired to get the secret present, of course,” he hurriedly corrected. 

“Ha, okay, okay, silly kid. Go upstairs and wait in my room while I tuck your brother into bed.” sans complied easily, despite his grumble of “i’m not a kid anymore,” as he left. Still sitting on the couch, Gaster took a deep breath in and out as his magic stirred excitedly. One thing left, and then he could join sans. 

“Alright, let’s get you tucked in,” The skeleton padded upstairs to his son’s bed, who had his blanket folded perfectly over his small body. 

“Can I see the present tomorrow, Papa?” Papyrus begged, his sockets wide and irresistible.

“Perhaps, if your brother is willing to share. It’s his call, though.”

“Aww! He’ll say no!” 

“Well then, that’s his choice. But don’t worry, when you’re old enough you’ll get it too, okay? Just be a little patient,” Gaster ran a hand over the kid’s smooth skull. Placatated for the moment, Papyrus nodded his assent, snuggling down further into his pillow. They clinked their teeth together in a goodnight’s kiss and he got up to leave the room. Pausing by the doorway, he turned back to the small skeleton watching him raptly. “Stay in bed, okay? I’m leaving my door open in case you need to shout for anything, not for you to spy.” 

“I won’t, Papa!” Papyrus assured, being the stickler for rules he was. “I promise!” 

“Good boy,” Gaster finally stepped out of the room, shutting the door softly behind him. Steeling his racing nerves, he walked down the hallway to his room, cracking the door a bit. 

sans laid in the middle of his bed, flat on his back as per usual, looking almost asleep. “sans? You might want to wake up, if you did still want the present, of course.” sans stirred, rubbing his eyes as he sat up.

“sorry,” he yawned. “your bed is so comfy.”

“I’m glad you think so,” Gaster chuckled, sitting beside him on the bed.

“where’s the present?” sans looked around, confused at the lack of items in his father’s hands. “is it hidden in here?”

“No, it’s not hidden. It’s more of...an activity. But first, take off your clothes please, all of them.” He waited as sans complied, not weirded out at all seeing how nudity wasn’t taboo in The Underground like it was with humans. sans was starting to worry that his special present was the one thing all kids dreaded getting: clothes.

Once sans threw them off to the side and got his attention back on his elder, Gaster continued. “Tell me, sans. How much do you know about sex?” His gaze raked up and down his small bones.

“i know what school teaches,” he blinked, clearly not expecting that. “sex can be for pleasure or to procreate, depending on what you’re doing.” His son had written notes, he was sure of it. School was the one area that sans showed interest in; the kid had a thirst for knowledge, taking after his father. 

“Good,” Gaster nodded, not missing the way sans sat up straighter, clearly pleased by the compliment. “Since you’re no longer in stripes, I thought you’d like a chance to experience it.”

“with you?” Gaster nodded once more. “wait, but i thought there were rules and guidelines,” sans furrowed his brow. “skeletons are considered full grown around thirty, but twenty is an acceptable age of consent if both parties are within their proper age groups. aren’t you a lot older than me? plus, i have seven more years until i’m 20…” He glanced away, clearly thinking things over in his head. Best to stop that wheel from spinning lest Gaster wanted this to go wrong. 

“Yes, very good observation,” Gaster began, “but those guidelines are based not only on physicality, but emotional maturity as well. I’m sure you’ve noticed, but you are a lot more mentally developed than kids your age. That is why I’m not concerned about the age guidelines.” He watched sans visibly think it over. 

“...i guess that makes sense,” he finally conceded. “i don’t want you to get in trouble, though. people will get mad we didn’t follow the rules.”

“Guidelines,” Gaster gently corrected. “Guidelines are flexible, rules are not.”

“okay. okay, sure,” sans started blushing a lovely cyan. Gaster had to resist cooing at his child. “uhm, why did- uh why do you want to have, uh… sex, with me?” 

“First times can be a disappointment, sometimes,” he rubbed sans’ back soothingly through his shirt. He felt sans relax minutely and hid a smile. “I simply wanted you to have some experience before you started meeting viable people. I thought it’d be a good way to introduce you to your after-stripe years. Unless you don’t want to, which of course if fine, sans.”

“...that sounds good,” he shyly admitted, refusing to make eye contact. 

“Alright, if you’re sure. How much experience do you have? It doesn’t have to be with other people.” He held his breathe, almost able to taste the answer he knew was coming. 

“i’ve...masturbated before,” sans admitted timidly. Oh, Gaster knew very well. How could he not notice the sudden need for privacy sans had when he hit puberty? How could he not know when he stood outside his door on occasion, straining to hear the muffled moans and wet noises from inside. 

“That’s a good start,” Gaster teased, rubbing a bit lower on his back. “Nothing else? Nothing at all?”

“wh- heh. mmmmmaybe i’ve kissed someone before?” The blush intensified and sans started to armadillo himself, wrapping his arms around his knees. 

“Was there tongue involved?” It was getting hard to keep his SOUL steady, his magic already roiling in his pelvis. 

sans shook his head slightly. “i was about pap’s age, i didn’t know how to form one yet.”

“Could I have a demonstration of what you know?” Gaster moved to sit back against the headboard, motioning for sans. “To see what your skill level is at.”

Looking determined to excel in this like he did everything else, sans crawled into his lap, eyes dilating slightly as he stared at his father’s mouth. When he glanced up to make sure it was okay, Gaster nodded and sans steeled himself, meeting their teeth at last. It was a bit anticlimactic, seeing as how they pecked each other all the time, as families often did. The only difference was that sans stayed for longer, his magic trying to spark between them. It still sent chills down Gaster’s spine and heat to his pelvis. He was instantly hard, shifting sans slightly so he wasn’t sitting on it directly, not yet. 

When the teen pulled back he was panting slightly. “how was that?” he asked. 

“You did well, for a closed mouth kiss. If you summon your tongue, I can further show you.”

There was a moment of concentration before his jaw opened somewhat difficulty, seeing how sans rarely bothers to open his mouth. Gaster couldn’t help his breathy groan when he greeted his son’s tongue with his own. Shying away at first, sans quickly adapted to the change in energy, pressing himself closed to his father, whimpering as he fisted his shirt tightly. 

Lowering him to the bed, Gaster hovers over him, roughly conquering his much smaller mouth. Instinctively sans’ legs move to wrap around the other’s hips as he shakes. His neck is sensitive, almost too sensitive if the way his spine goes rigid says anything. Gaster’s breath warms his own face as he crowds the small skeleton beneath him. His son’s SOUL is racing and pulsing below his sternum as he runs his tongue up it and, unsurprisingly, sans cums with a shout of alarm. 

Not wanting to overwhelm his eldest just yet, Gaster blessedly pulls back, giving sans a moment to collect himself. Said skeleton’s body was still shuddering with the aftershocks of his orgasm. Agitated magic swirled around his body, but nothing had formed yet. Silvery SOUL fluid slowly dripped down his spine to pool into a small puddle on the sheets below. 

After several long, torturous moments, sans finally opened his eyes again, the lights still hazy. Gaster was presented with a small smile and a quiet, “thank you, that was really good.” Stifling a laugh at his cute naiveness, he assured sans there was more to come. Pun intended. 

sans debated the meaning of the words for a moment, still trying to catch his breath. “do you think i can make extra parts like that?” he finally asked. 

“Of course, son,” Gaster was quick to assure. “You have excellent magic output. I am one hundred percent certain that you can.” As he’s speaking he slowly drags his hands down to the boy’s pelvis, slyly thumbing his pubic symphysis. sans’ voice cracks on a moan, his hips arching up into his touch despite the sensitivity. 

“it feels a lot different, when someone else is doing it,” he remarks idly, passively trying to direct his raging magic lower. Cyan slowly bleeds into the small cradle of his pelvis as sans fists the bedsheets. There was no doubt that bare magic carries intent better than bone. 

“It’s the partner’s SOUL reacting,” Gaster answered just as distractedly. He had crooked his fingers into the coalescing magic in his pelvic girdle, trying to bribe it to shape into something he could fuck. At first he could feel his son’s magic aching to obey, but it wasn’t developed enough to have that much control, and instead defaulted to something his young son was used to. “Is this what you masturbate with?” Giving up for the moment, Gaster took the small dick in between his thumb and forefinger, rolling it experimentally.

Hiding his face in his jacket-clad arms, sans made a high-pitched keening noise, his hips thrusting on their own, irregular pumps as he’s brought very quickly closer and closer to climax. When Gaster pauses so he can answer sans gives a very small nod, eventually adding to that. “i used to default to, uh. partially solidified magic? kind of like slime that stuck to one area at a time,” he admitted. “the penis is a recent thing. it’s a lot less messy.”

“I bet.” Humming, Gaster gave a soft tug, almost like an afterthought. “Have you ever formed a cavity of any kind?” 

“the slime was malleable, but otherwise no,” sans panted, attempting to buck against Gaster’s fingers for stimulation. 

“Here.” A phalange was stuck through the still unsettled magic beneath his son’s small dick, all the way up to the knuckle. “Try to wrap your magic around my finger.”

The young magic tried and failed to do what Gaster wanted multiple times, too unused to invading pleasure at such a young age. Eventually though, sans succeeded. Crooking his fingers up, Gaster explored the tight hole thoughtfully as sans gasped and dragged his heels against the blankets. Slowly, as to not pop the magic with the strain, he added another finger, then another after a few minutes. He lets sans cum now, while he's shaking and sweating. In response his small prick is dropped so Gaster could focused on the part that would bring himself the most pleasure. 

“Usually, there’s a more sensitive area in this kind of construct,” he poked near the back of the passage, raking his fingers upward, “here.” The tips of his fingers were almost zapped with how quickly magic was directed there, and sans cried brokenly, clearly having succeeded his goal. 

“ffffuck!” he whimpered, panting heavily. 

“Now son, you know vulgar language is not allowed in my house,” Came the sly reply. “I will give you a pass this once, as it is your first time,” he smirked. Gaster could practically taste him getting closer to cumming, and removes his finger, heedless of the protest that’s received.

Struggling to his knees, Gaster had to remind himself to slow down, breathing heavily as he unclasped his belt to free his writhing magic. His default was a tentacle of sorts, which was already moist and ready to go, moving around to find it’s target. Looking up, he found sans watching intently, and when he beckoned the smaller his lap was eagerly climbed into. sans looked beautiful, with tears streaking down his cheeks, drool pooling in the corner of his mouth. 

He sat on his father’s thighs, grimacing as he looked down. “i don’t think that’ll fit,” he panted, his hand hovering like he wanted to touch it. Gaster took his hand, gently dragging it down to the base of the tentacle. sans’ breath hitched as he started stroking it on his own.

“Magic is more pliable than you think, as well as self lubricating. It will fit.” Smirking, Gaster flipped sans onto his hands and knees. sans looked at him upside down from between his own legs. 

“what was that for?” 

“This is a superior position, in my opinion of course.” Raising to his knees, Gaster shuffled closer, his appendage moving with it’s own, the tip straining forward to impale itself in his son’s magic. He held back, positioning himself just out of reach, soaking up the younger’s needy noises as he ran a thumb over his entrance. After a few more swipes, sans started to rock back and Gaster decided it was time. Without further ado, Gaster slowly inched forward, letting himself fill sans rather quickly for his first time. The entrance was smooth considering how gradually the girth increased, but sans sucked in a breath, squinting at the bedspread in discomfort. 

“dad, it hurts…” he managed, squeaking in alarm when Gaster withdrew then slapped their hips together again. 

“Does it?” Groaning, Gaster restrained himself from plowing into him just yet. While he knew it didn’t hurt, he didn’t want to scare sans off so soon. 

“...no,” he eventually admitted. “i don’t see why people find this so fun, though.”

“Give it a moment, it will start to feel good.” 

The only sound for a minute was Gaster’s stifled moans and the slap of their magic. sans was so tight around him, his virginal magic too young to expand and flex around him properly. He could feel resistance as sans would randomly clench down, obviously trying to get used to the feeling. He had been waiting for this for so long and the reality was better than anything he could’ve imagined. 

Slowly, sans started to moan, soft and unsure. His fathers tentacle was writhing inside of him, desperate to stay inside even as Gaster withdrew. Finally, it succeeded in finding the spot Father had helped him make, pressing against it with persistence. He joined his dad with gasps and moans as it did indeed start to feel good. It felt amazing, in fact. The yells of ‘fuck!’ started up again, but his father said nothing. The intent behind Dad’s thrusts made him cum again very quickly, his body unable to make sense of this new stimulation. He had never had a lot of stamina, that was more Papyrus’ thing, and after the first orgasm he had wanted to stop, but his father was so overpowering, his desires fueling his own as he was swept along for the ride. 

The continued thrusting started to bordered on painful now, and his arms, which felt weak and shaky, collapsed underneath him, bringing his face to press against the bed. He knew his legs would’ve followed if Gaster wasn’t holding his hips up, angling him for his pleasure. Drifting off, sans no longer felt like he was a part of this. He felt somewhere else, watching his body being drilled into, safe away from the stimulation. The feeling went over and through him in waves, bringing him small spikes of pleasure, as well as incredible discomfort. Not knowing if this would hurt or help due to overstimulation, he brought a shaky hand down to his penis, rubbing it frantically. His wish of it turning the stimulation back into pleasure came true, sort of. It was so overwhelming and he belatedly realized that he was wailing into the blankets, his fingers coiled tight, sure to wrinkle the sheets. 

His fourth and final orgasm of the night slammed into him like a very solid wall; his body simply hit it and bounced off, hitting the ground as well. sans screamed, higher pitched than Gaster had ever heard, and the older skeleton checked with a hand to see if he had cum from his penis. Letting out a small ‘haaah’ when his hand came back no wetter than magic generally was, what with how young sans was, Gaster leant over his boy, growling as he felt his own peak approached. If he was fully cognizant at the moment, sans would’ve been embarrassed. He was slightly proud of his deepening voice, but he was not, in fact, aware of anything anymore. His mind had whited out, his body not responding to himself in a desperate attempt to save itself from the overstimulation. 

Unconsciously, sans’ mind ran on without him, leaving him in the dust. He started whimpering and yelling into the blankets, a steady stream of “no more, no more!”. Heedless of his son’s pleas, Gaster pinned him flat to the bed, unable to help himself as he bit down right at the top of his bare scapula. He came to sans’ last shrill shriek, practically roaring as he buried himself in deep, his tentacle stiffening as magic filled the tube, then releasing it in large bursts, filling sans completely. Without meaning to, he gripped sans’ shoulders tight, shaking him as he pushed him back onto his tentacle as he came down, pumping the last of his seed into his young child. 

Flopping unceremoniously to the side, Gaster allowed the both of them to catch their breath. sans was making small, wordless noises as if he were unable to help himself. Sitting up he looked at his son's face. Yep, no awareness whatsoever. He felt triumphant, having caused this. Now his only hope was that sans, if left to his own devices, would start to miss sex, even if it had been painful. Monsters were very good at forgiving and forgetting; they desired and craved connection and positivity.

Arranging his limp son so his head was resting on the pillows, he paused for a moment to watch his constructs disappearing, cum splashing everywhere. Dragging a finger through his own cum, he licked it off of his hand, finally glancing to his youngest son hiding by the door. 

Papyrus squeaked in alarm, ducking out of sight. Before he could get very far Gaster called after him. “Papyrus, come here.” A very sheepish child slowly trotted into the room, already looking chastised for having broken a rule. 

“I’m sorry,” he started, his eyesockets going wide when Gaster patted the bed next to him. With only a moment's hesitation, Papyrus leapt onto the bed, hugging his dad tightly. “I’m sorry, Papa! sans sounded hurt and I wanted to make sure he was okay!”

“It’s quite alright my son, I can’t blame you for being worried,” he clanked his teeth to the littlest skeleton’s cheekbone. “However, I can assure you that sans was having a lot of fun. That’s how your body reacts when it feels very good.”

Papyrus gasped. “I want to feel good! Do it to me next!” 

“Not yet, Papyrus,” Gaster took the small invasive hands with his own. “You have to be thirteen. You can’t be in stripes when you do this with me, understand? And we can’t talk about this outside of our home. It’s one of those topics that stays between family. It’s not proper to talk about it to the public.”

“Okay,” he nodded, trying to look very mature. 

“Good boy,” he purred, pushing on his coccyx to bring him closer. He thumbed it softly but Papyrus didn’t seem to notice, instead turning to the mess on the bed.

“What is this? It came out of sans.”

“I actually put it into sans,” Gaster sighed in satisfaction, leaning against the headboard again, this time with a different son in his lap. “It’s called semen. It’s spent magic that’s released when you have sex with someone.”

“Oh that’s what that was?! I didn’t recognize it, it’s a lot different seeing it rather than it being taught in class.” He looked thoughtful for a moment. “Aren’t adults not allowed to have sex with children? My teacher says you can get in a lot of trouble,” Papyrus looked really concerned, face crinkling in distress.

“It’s alright,” he continued to rub soothingly along his small, cute tailbone. “Your brother and I have already talked about the rules. He’s mature enough to handle it, I won’t get into any trouble.” Gaster smiled gently before turning serious again. “However, you still mustn't mention it anyway, okay? You would get in trouble for talking about it, your teacher and I would be disappointed.”

Papyrus teared up at that, shaking his head at the same time he lunged to hug his father. “I won’t, I promise! I don’t want you to be mad at me!” 

“That’s good, then,” Gaster kissed the top of his skull this time. “...You may not be mature enough yet for sex, but would you like to try this?” He dipped his finger in the drying magic, holding it up to Papyrus’ face. 

“What does it taste like?” he scrunched his face up at the smell.

“Well, I supposed it tastes like my magic. It makes you feel how my magic makes you feel too.”

Papyrus beamed. “You make me feel safe!” Without further ado, he brought his open mouth to his finger, the agitated magic in his mouth quickly latching onto it. His sockets widened again, then drooped as he moaned. It took all of Gaster’s restraint not to jump his youngest child. The intent of the cum was clearly affecting him, even if he didn’t know it. Magic licked cum off of his finger, a formless haze of orange condensing on the roof of his mouth. Just as sans had been unable to form a tongue at this age, Papyrus still hadn’t gotten the hang of it yet. No matter, though, this was just as good. 

“It makes me feel tingly,” the child concluded when he pulled off of his father’s finger. Curiously, he dragged his own fingers through the rest of the liquid magic, scooping it into his mouth. He moaned again, higher and drawn out. It was enough to make Gaster hard again, but he simply dispelled it, not without regret. Now was not the time, unfortunately. This was enough pushing for one day. 

“I’m glad you’re enjoying it, son. It’s time for bed now.” Shifting the rest of the way out of his pants, Gaster pulled the blankets over all three of them, opening his arms up as Papyrus snuggled in close, his small pajama-clad legs resting against his side. sans was snoozing away at his other side, oblivious to the world. Both felt warm and Gaster had to take a few calming breaths lest his magic form again. 

“I feel so full,” Papyrus yawned, slowly drifting off. ‘I’m sure sans does too’ Gaster thought with wry amusement. 

“Goodnight, Papyrus,” Gaster murmured.

“You have to say goodnight to sans too.”

“Goodnight, sans,” he chuckled. “Now go to sleep.”

“Okay... I love you…” he whispered, finally dropping off. 

As Gaster held both of his kids, one very naked and smelling of sex, the other small and vunerable against him, his face still flushed, he felt a shiver of excitement race down his spine. Patience. It would all come together in due time, he reminded himself, already imagining next time.


	2. Chapter 2

**Summary for the Chapter:**

> papyrus gets a taste

**Notes for the Chapter:**

> contrary to popular belief, this chapter doesn't have a ton of papyrus time. i hope you can understand why as you read :0 this chapter kicked my butt and if i try to revise it it's never getting done xp
> 
> (tags updated for suicidal thoughts)

It had been a week and a half since he and Dad had sex. Time had gone on normally; they ate meals as a family, sans and Papyrus went to school as normal, their routine was virtually unchanged. sans had been in the middle of a school project with a group of friends and he was grateful that he got to spend time away from home working on it. Not that he was uncomfortable being home, of course not that’d be stupid. Nothing was wrong.

Nothing was wrong, but something  _ felt  _ wrong. He didn’t know what but somewhere in his SOUL felt off. Maybe it was just him that was wrong? He was thirteen now, perhaps he was just growing out of family time. 

Either way, Sans spent most of his time at friends’ houses, sometimes sleeping over at Alphys’ when they stayed up too late reading trashy romance novels. Unfortunately, even that started to very quickly grate at him. The stories that he once listened to her read with fondness now irritated him, to the point where he needed to leave before he blew up. At her? Perhaps. It felt like just a general combustion though, and sans had no idea why. 

Everything was bothering him, literally everything. Something as simple as the shop being out of something he wanted made him want to yell and scream and throw a tantrum. Teachers and books had mentioned heightened emotions as a side effect of puberty but sans didn’t think they meant to this extent. Besides, he had started puberty about a year ago, and he had never been this irate.

Like everything else, sans pushed it to the side; if he ignored the problem it would go away, right? 

After school, instead of picking Papyrus up from his class and walking home with him and Dad, as he usually did, he decided to wander around the Underground. Their school was in the heart of New Home, a place easy to get lost in. He had managed to duck out of his classroom quickly, dodging any questions his friends tried to ask him, speeding off in the complete opposite direction of his house. 

Spending time at the markets always relaxed him, and sans sat at a bench in the middle of the bustling city for a while, slowly eating the sour candy he had bought himself. Normally, he’d pick something up for Papyrus too, Angel knew that kid had a ravenous sweet tooth, but today he deliberately didn’t. Feeling a tiny bit guilty didn’t dampen the anger that swirled in his ribcage. His brother had been pestering him lately, insisting he share his present. What if he didn’t want to?! He shouldn’t have to share everything!! 

He loved his brother, he did, but the kid needed to learn some boundaries. 

So he sat here and watched people go about their business. He tried to stay focused in the now, but as his mind often did nowadays, it wandered to the events that transpired two weeks ago. Weirdly enough, whenever he thought about it, it wasn’t in clear memories. Instead it was a haze of emotions and he was unable to recall most of it, even before they actually had sex. Poking and prodding at his jumbled memories just made him want to cry, for whatever reason. God, he really was a mess of hormones. 

Well, he was able to pick out a few feelings. He felt guilty, guilty that he probably let down his father, guilty that it didn’t exactly feel good (that much he was able to remember). And yet, despite knowing it wasn’t a pleasant experience, his body started to heat up at the reminder. Pushing tears back, sans got up to leave, shoving the wrapper into his inventory to throw away later. 

This was getting ridiculous, really. That random sadness turned to anger as it often did now, but he didn’t even know what he was angry at! 

Glancing at his chiming phone, he rolled his eyelights and turned his phone completely off when he saw it was the group chat - someone asking him if he’d be by tonight to help finish up. He would not, but it’s not like they needed to know. School was starting to become an annoyane, to the point where he didn’t even want to go anymore. Part of him felt panic in that, because he used to be so excited about it, so happy that he got into higher level classes, happy that he had a set path in science. He wanted nothing to do with it now. What would he do with his life? Mope around, probably. Because everything’s solved this way, he thought with a scowl. 

Kicking up red dust and rocks, he slowly made his way home, shucking off his beloved jacket once the temperature outside started to match the inside. Unlocking the front door, he threw his backpack down, eager to get to his room but Papyrus’ happy greeting drew his father into the room too. 

“hey, pap,” he muttered, his chest feeling tight as he crossed the room, heading up the stairs. 

“Can we hang out tonight?” Papyrus pleaded, standing up to chase after him. “We can finish that puzzle! Or we could read, or play fort! We could finally try what you and Papa did-!” He latched onto sans’ arm and his SOUL jumped to his throat, his limit reached.

Yanking his arm away from him, sans pushed Papyrus away when he stumbled into him, clearly not expecting that. “no! leave me alone!” he yelled in full view of their alarmed father before running upstairs, slamming the door to his room. His breaths felt shuddery as he leaned back against the door and locked it, sullen tears finally finding their way down his face. Not bothering to turn on the light, he stubbornly wiped at them on his way to his bed, flopping into it when his knees hit the frame. 

That was the first time in years sans had yelled at Papyrus like that and he already felt nauseous that he hurt his baby brother. He loved him so much, how could he yell at him like that? How could he push him? 

Guilt forced him under his blankets, his head under his pillow as his tears quickly dried up, leaving him feeling empty. So what if he hurt Papyrus’ feelings. So what if he didn’t go to school ever again or his friends started to hate him. Who cared if he dusted alone in his room,  _ who cared?! _

He was allowed to wallow for a couple of hours, unable to find sleep no matter how desperately he wanted to. In spite of everything that had just happened, the heated feeling inside of him only got worse, dropping down to between his legs. Self-loathing made him grit his teeth, a hand snaking down to paw at himself. It was hot and wet inside his shorts, but nothing had formed yet. Good. Forcing his magic to avoid taking a physical form, sans scraped at his pubic symphysis, soft sounds escaping him. He came once after a few minutes and kept going. The pleasure kept cresting and receding, never quite enough to push him off the edge but he still continued without relief. His pelvis was already raw and chafed from the previous times he did this, but he didn’t really know what else to do, so he rubbed himself sore, desperate to make the dreaded heat go away. 

There was a soft knock at his door, then another when he didn’t respond to his father’s calls. After a heartbeat there was a click as his door was unlocked. “sans?” Father called again, poking his head into the room. When he caught sight of the sad lump on the bed he entered the room, shutting the room in darkness as he closed the door behind him. “sans, we need to talk.”

Despite the firm tone, the sentence was said softly, but sans still felt a stab of fear run down his spine. He had stopped touching himself at the first knock, his hand now fisted tightly to his shirt. Unbidden, disappointed tears welled up again. Why was he scared of his dad? Why was he feeling like this, it was literally driving him insane. “what,” he sulked, voice muffled by his protective covering. 

He felt Dad sit on the end of his bed and place a hand on his covered foot. SOUL leaping up to his throat, sans yanked his foot back quickly, filled with the vision of his dad yanking his foot, and subsequently him, right off the bed. Afterward he felt stupid; where had that come from? Dad had never given him a reason to think that he’d hurt him, never raised a hand to them. 

Seemingly shocked at the violent reaction, Gaster gently lowered his hand to his own thigh instead. “...I am not sure what’s going on, son, but I’d like to discuss it.”

“nothing’s going on,” sans mumbled, because 'i don't know' didn't feel like an answer.  


“I’m not sure that’s true, sans.” Gaster sighed, and tears sprang back to sans’ sockets. Great, here he went again, letting his beloved father down. “Can you please come out? So we can talk this through? I want to help you, I really do. I’m just not sure where to start.”

Thinking on it for a moment, sans took a deep breath and uncovered himself, rubbing his left eyesocket as he sat up. Staying silent, he let his dad start the conversation, as he didn’t know what to say. 

“What happened earlier? You haven’t lashed out at your brother since you were little. Did he do something that angered you?” Gaster said after debating his words for a minute. 

“no? i don’t know,” sans shrugged, dragging his blanket free to tug over his shoulders. “he didn’t really do anything. i’m just. annoyed all the time now, i don’t know why?” He shrugged again. 

“Well, when did this start?” Gaster sighed, already knowing the answer. 

“....about a week ago,” sans confessed, squeezing his eyes shut to prevent himself from crying again. Waves of shame and self-hatred rolled over him, threatening to drag him down as he silently panicked, knowing his father would be upset with him.

“Was it because of what happened on your birthday, sans?” Came the soft reply, and when sans nodded Gaster seemed resigned. “I am...so sorry, my son.”

Confused, sans looked up at him. “wait, why are you sorry?”

Shaking his head, Gaster rubbed at his face. “It’s my job as the adult and as your father to protect you. I thought you’d be mature enough to be able to handle sex, but I miscalculated. Perhaps you are too young for it.” Indignation swirled in sans’ SOUL as he started to get worked up again, and Father’s next words made it flare in agitation. “I understand if I make you uncomfortable now,and if you’d like to tell another adult what happened, I’m more than okay with accepting the consequences.”

“what?? no, it- you didn’t-” While sans struggled to find the words to his thoughts, Gaster stared at him, trying his best to shove down the laughter that wanted to bubble up. There really shouldn’t be this much fun in manipulating children, it was just the fact that he knew exactly how sans would react that he found humor in. “you didn’t do anything wrong!” sans finally spat out, glaring up at him. “it’s me that’s getting worked up about this, i’m just too stupid to handle things like i should be-”

“Oh, sans, no,” Gaster crooned, wrapping his son in an embrace. He took note of how tense sans was, as well as the way he forced himself to relax. “No, it’s not your fault either, and you are not stupid. You’re a very bright child, you might just need more time to adjust.”

“...maybe,” sans sighed, relaxing even further against Dad, rubbing his face into his sweater, inhaling his scent. “i… i did like it,” he lied. 

“I’m sure you did,” Gaster chuckled. “It’s okay to need time to process. However, it’s not okay to treat your brother like that. I’m sure you know you need to make it right.”

“yeah,” sans sighed and left it like that for awhile, hugging his dad tightly as the uncomfortable feeling finally took a backseat. However, sitting in his lap like this, it gave his body other ideas, his previously ignored problem returning in full force. 

Unable to resist a smirk, Gaster felt sans squirming uncomfortably, his body heated against his own. “Is something wrong, son?” When no immediate reply came, he smoothed a hand down his kid’s back. “Remember, you can come to me with anything. I will always do my best to work with you.”

“...i’ve been feeling. uhm. horny,” he whispered the last word, his face flushing bright blue. “a lot lately. randomly, and it won’t stop or go away.”

“Ah, that’s a natural response to finally getting fucked,” Gaster laughed at sans’ indignant sputtering. He calmed them both down by resuming his light petting, rocking his eldest son slightly. “Seriously, it’s completely natural. It should calm down if you find a regular outlet.”

“masturbating isn’t working,” sans mumbled and his father nodded sagely. 

“It might not be enough now that you’ve gotten a taste of better stuff.” Tilting his head, Gaster seemed to contemplate something. “I know you’re probably tired of Papyrus asking, but it could benefit you both if you were to share some of that energy with him.” sans stiffened again, a shard of fear lodging in his SOUL for some reason. “You could make it up to him, what happened earlier, and help yourself at the same time.”

“he’s too young,” sans huffed out, feeling like crying again as he struggled to breathe. 

“Easy, son,” Gaster readjusted his grip on him, snuggling him closer. “I’m not saying have sex with him, maybe just make him feel good, let him make you feel good. That much he can handle, I’m certain of it.” 

sans didn’t want to point out that he was certain sans could handle it too, didn’t want to upset his father when he clearly was trying to get through this with him. “You don’t have to decide now,” Gaster continued, finally putting him down, standing to leave. “Just think about it. Papyrus thinks you hate him,” he said pointedly, his sharp words not matching his soft demeanor, closing the door quietly behind him. 

Anxiety made sans nauseous again as he stared at the door, his breaths coming out harder and harder until he forced himself to curl up, face down on the bed. Taking a deep breath in, he let it out in a frustrated scream, his fingers coming up to clutch at his head. That talk hadn’t helped at all, just made him feel worse. 

Now, more than ever, he didn’t know what to do.

  
  
  


Later that evening, around dinnertime, sans plodded down the stairs, pointedly not making eye contact with his family. He sat down at his usual spot where a plate waited for him, some leftovers from the other day. Papyrus and Gaster had clearly been talking when he came down but now both were silent, and sadness radiated from his little brother, making sans’ food taste bland. 

They ate dinner quietly, and Gaster finished first, moving to clean up his plate. Papyrus shoveled more food in his mouth, standing to follow, clearly not wanting to be left alone with sans but the older skeleton reached out, gripping his wrist softly. “i’m sorry, pap,” sans said, and Papyrus stared at him for a moment before bursting into tears, darting around the table to fall against him in a loose hug. sans barely stopped himself from shoving him back off.

“I’m sorry, sans!” he wailed, not one for much tact. “I don’t know what I did to make you so mad but I’m sorry!! I won’t do it again, please don’t hate me!” 

Tears started to dot his sockets again. “pap, i would never hate you, ever. you didn’t do anything… i’m just having a bad day and took it out on you.” Papyrus said nothing, hugging him tighter as he buried his face in his neck, sniffling sadly. “is there anything i can do to make you feel better?”

Shrugging, Papyrus hesitantly pulled back, rubbing his face. “I don’t know.”

Glancing up at his dad, sans tried not to glower at him as Dad pointedly looked at him. “...i could suggest something? we could, uhm. do the stuff you wanted? the present stuff...” he mumbled. Papyrus’ innocent, happy, curious expression made his chest tight again, but when their father ushered them out of the room he went, clutching Papyrus’ hand tightly in his.

At his direction the children sat on the plush carpet, staring up at Father, waiting for direction. Debating for a moment, Gaster pulled Papyrus up into his lap, going to kiss him, which Papyrus happily complied, only for it to turn confusing when Papa wouldn’t let him pull back from their usual peck. Gaster kissed him thoroughly, and when he finally pulled away Papyrus was gasping for air, seemingly dazed. “That was a grown up kiss,” was all he said, It seemed to clear the youngest’s head a little, for he perked right back up.

“Wowie! I didn’t know kisses could be like that!” 

“Yes, well now you know,” Gaster chuckled, sliding him off his lap. “I want you to try kissing sans that way.”

sans’ SOUL froze in his chest when Papyrus turned his attention to him, sitting back down next to him. When he leaned in sans leaned away, looking at their father fearfully.

“Don’t worry, son,” Gaster soothed. “You won’t get in trouble for kissing your brother. You won’t have sex with him.”

“Aw!” Papyrus whined, but quickly forgot about it when sans finally inched forward, bringing their teeth together. sans kissed his baby brother, his eyes pinched shut tightly and he tried to think of anything else, anything but the body against his. 

He heard Dad pointedly clear his throat and sans broke the kiss to glance up at him. “This is supposed to be an apology, sans,” he said, and looking from a disapproving look to the disappointed look on Pap’s face made him push down tears again. Without so much as a sound he leaned back in, hesitantly swiping his tongue across Papyrus’ teeth even as his SOUL roiled with nausea. 

Papyrus made a small sound into the kiss and pushed himself even closer to sans, practically crawling into his lap. He hugged the elder’s middle tightly as he made his little noises, and despite the bad feelings, it was more than enough for heat to flare in sans’ core. 

Just as sans had been unable when he was Papyrus’ age, said skeleton couldn't form a tongue. That didn’t stop thick strands of magic from tangling with his own solidified magic, though. Exploring Pap’s mouth was interesting, different than Father’s. Their kiss was humid, sloppily done as Papyrus moaned and writhed against him. Unwillingly, it made sans’ magic start to solidify in other places, and seeing as how he was on his lap, Papyrus took notice. 

He pulled back, panting, to look down at his older brother’s lap, brow furrowed in concentration. Experimentally, he wiggled left to right, and sans gasped, clutching his hips tightly. He didn’t hold too hard, not wanting to hurt him again, so Papyrus was free to continue, clearly very determined to help his brother fall apart. Subconsciously, sans started to rock up into him, his penis getting harder against the small clothed pelvis on top of him. 

It didn’t take long until sans was cumming dry, whimpering as he gave a last few thrusts against his baby brother, his arms finally falling limp against his sides. “Did you have an orgasm?” Papyrus asked sweetly. While school doesn’t teach that in depth for his age, Papyrus had a very smart father, who could teach him things himself, like engineering and sex. They had watched many videos together in preparation for sans to finally share his present. He prided himself on being very smart for his age. 

sans, however, didn’t respond, rubbing his wet face against his shoulder, trying his best to shy away from the skeleton on his lap. Taking pity on him, Gaster called him and sans eagerly scrambled away from the source of his guilt. 

“He’s crying,” Papyrus crawled up to the couch on his knees, trying to see sans’ face as he hid against Dad. “Did he not like it?”

“Sometime’s sex can be overwhelming, especially when you’re still getting used to it,” Gaster explained as sans shook, running a hand down his spine. “Now sans, calm down, okay? It was a bit rude to cum while you’re supposed to be apologizing to your brother.” 

His words were tacks thrown into the maelstrom that were his emotions. As he grew more upset, his outside dissociated, and he became eerily calm very quickly. “There we go,” Gaster cooed as he guided sans up to look at him. “Now, I am going to show you how to please Papyrus, okay? You won’t have sex with him, just make him feel good. That’s not illegal, no one will get in trouble.”

Somehow sans doubted that, but he scooted down when Father guided him anyway, waiting patiently as he pulled off his pants. Papyrus breathed a soft ‘oooo’ as Dad’s pelvis was exposed. It wasn’t odd, to be naked in their society, but under the circumstances, it was no doubt that Papyrus was seeing it in a new light. Gaster preened a bit under the attention, running a finger over the sensitive bones. 

“Since Papyrus won’t be able to summon anything, I’m going to show you where to touch to make him feel good,” he explained, noting the detached look in sans’ eyelights as he stared down at his wandering fingers. “You need to use your tongue, try right here,” he traced his hand over his ischium, and to his delight sans obeyed without any hesitation. 

He couldn’t help his sighs and moans as he guided sans all over his pelvis, his symphysis and foramen, sacrum and coccyx. His boy really was a natural, and all too soon he had to stop before he came. He needed patience, so with great reluctance, he pushed sans away. “Good boy, now go try that on your brother.” In spite of himself, those words made sans preen and he slid to the floor to kneel back beside Papyrus. After some debate, sans laid down on his front, an eager young brother sitting in front of him, his pants already off. 

Taking in a deep, shuddering breath, sans examined his baby brothers small bones with detached focus, his mind not really absorbing what he saw, just that his pelvis was so small, too small. Papyrus tried to squirm forward, his eyes bright with anticipation and sans couldn’t hold eye contact, so instead he leaned forward, running his tongue right over his pubic symphysis. 

Papyrus stiffened but didn’t move away, his mouth reflexively making a surprised ‘oh’. After taking a moment to make sure he was okay, sans continued, giving small kitten licks all over his pelvis. His brother squirmed uncomfortably at odd intervals, but everytime sans lifted his head Father was there to guide him back down, reminding him that this was an apology. 

His body was having no issues getting on board with this, even if sans himself was. His magic was still formed and his hips twitched on their own occasionally, the friction making him moan softly. Papyrus seemed to not know what to make of this, oscillating between pushing his hips forward and squirming to get away. He was letting out little gasps and moans of his own, eventually falling onto his back, looking up sightlessly at the ceiling, his hands over his drooling mouth. “Oh, brother... that feels good,” he finally settled on, again meeting sans’ licks with his own movements. 

sans felt a flash of affection for his brother and, still licking along the front of his pelvis, added a couple of sly fingers running up and down his coccyx. “Ah!” Papyrus jolted, hands flying down to grip the carpet tightly. “That’s- that’s, oh my god,” he moaned, closing his eyes and tilting his head back as sans put some more effort into it now that he had proof Papyrus actually liked it. 

The praise made him feel lightheaded and high and sans felt like could never live without it now. Crooking a couple of fingers, he moved to into his baby brother’s small foramen, the one imbedded in his pubic arch. sans fed off of Pap’s energy, getting closer and closer to an orgasm despite not being touched.   


Hearing slick sounds, sans came up for air, looking back at his father, who was openly oogling now. sans blushed heavily, looking away in embarrassment when he saw Dad fingering his own pussy, legs spread for him to see. Gaster chuckled, pushing sans back down to Papyrus’ waiting form with a foot. 

It was getting very hot and moist down there, magic thickening and sliding down his bones like honey. sans lapped it all up between gasps, trying desperately to breathe as he practically drowned in his brother’s magic. He didn’t think he could last any longer, he was surprised Papyrus had lasted this long, what with how he was squirming on the carpet, crying out repeatedly as the sensations got more intense. The skeleton was shaking pretty badly, one hand tearing into the carpet, the other clasped onto sans’ shoulder. It stung a bit, but it helped keep him grounded so sans didn’t mind. 

Pap’s slim thighs were threatening to crush his skull, so sans used his elbows to pin the trembling femurs flat to the ground, changing the angle of his hands. He reached out blindly for the other, and finally Papyrus took his hand in his own. With a slight scrape of his teeth against his symphysis one last time, Papyrus finally came, his high pitched moans practically screams. His SOUL seemed to swell and burst, coating the inside of his tiny ribcage.

sans tried to gentle him through it but it very quickly proved to be too much. Papyrus scrambled away from him backward before collapsing again, their hands still intertwined. “you okay?” sans asked once his breath was a bit steadier. 

“I think so,” came the reply. Papyrus seemed out of it, staring at the ceiling with wide eye sockets. Not knowing how to help, sans just squeezed his hand, hopefully grounding his brother in the process. It was comforting to him as well, until he remembered the uncomfortable feeling of his penis rubbing against the inside of his shorts. Trying to shift discreetly only made it pinch and he winced, reaching down to alleviate the pressure. 

Alarmingly, tears had started to slip out of Papyrus, as did large, dramatic breaths. sans sat up quickly, moving closer to him, clutching his hand tightly. “paps?!” 

“It felt good,” Papyrus tried to explain, rubbing the tears away angrily. “I don’t know why I’m crying?”

“Come here, children.” Gaster had sat up as well, his arousal pressed against the couch and he held open his arms. sans helped Papyrus up and they both quickly moved for comfort, cuddling in close when their father embraced them. “You both did very well,” he said, clacking a kiss over both of their heads. “It’s okay to cry, Papyrus. As I said before when sans did, mature pleasures can be overwhelming sometimes, especially if it’s your first time sharing it with someone else. Do you have an idea of how to make it feel better?” Gaster hummed, rubbing their backs slowly as his cunt soaked through their sofa.

“A bubble bath?” Papyrus unsurprisingly suggested. He loved bubble baths, especially when their bath toys were involved. It was one of the few places he could stand to have his gloves off. 

“That’s a very good idea!” Gaster crooned at the childish suggestion, and sans shoved the spike of jealousy he felt down, rubbing his angry expression against Dad’s shoulder, hoping to smoothe it out. “Why don’t you go get that started?”

“Okay!” Papyrus sniffled one last time, rubbing his face before smiling brightly. He got up to race to the bathroom, but almost collapsed on his wobbly legs. Standing up again, he went more carefully this time and Gaster tried not to laugh as his little boy walked away like a newborn deer. sans was pulling away from him too, presumably to go sit in the bath too, but Gaster held onto him. 

“It’s okay to feel jealous, sans,” Father whispered against his skull, and sans’ eyes widened, breath quickening again. “It’s okay, my son,” he pulled him all the way into his lap. “Do you remember when Papyrus was born? And you were worried I would love you less or have less time for you?” he waited until sans nodded, staring resolutely at his Dad’s shirt, the one currently twisted in his small fist. “What I said to you then still stands - I will always love you. If you need some personal time with me, I won’t mind at all. You will always be my special boy,” Gaster finished his sentence with a soft kiss against sans’ teeth. The younger skeleton hesitated, then brushed their teeth again, magic wanting to cling together like sparks of static between them. 

sans still felt very uneasy, but it was easier to ignore when his dad held him like this, like he was important, treasured. As they sat there and kissed, sans felt one of his father’s hands snake in between them again to rub at his own entrance. Blushing heavily, sans was unable to resist breaking the kiss to look down at their hips. He clearly had a small bulge underneath his shorts and it almost pressed against Father’s pussy. Gaster trailed a hand against that as well and sans gasped, his hips hitching forward. 

When Gaster heaved sans to his feet, sans clasped onto his shoulders uncertainly as he worked to tug down his pants before manhandling the small skeleton back onto the couch right in between Dad’s legs. Their ecto was so close now, and almost without meaning to, sans moved closer, his small prick catching against the rim of Dad’s clit. He whimpered at the weird feeling - he’d never put his bare penis against another person before.

“Come here,” Gaster murmured, and looking at his face, sans’ SOUL raced at the half-lidded expression. Shuffling closer on his knees, he waited in anticipation while Gaster took his penis between his thumb and forefinger again, tugging gently to make it get harder. sans whimpered into his closed mouth, his body definitely moving on it’s own now, looking for more of the overbearing stimulation. Finally, after what seemed like ages, Gaster positioned him so the head of his dick rested against his hole, then he retracted his hand, leaning back on his elbows. 

“Well?” He smirked up at sans. “Go on, then. I have a feeling you want to.” For a moment, anxiety weighed on him like bricks stacked in his chest, but sans cleared all thoughts from his head, counting to three before he pushed inside. 

sans gasped as Dad’s tight heat surrounded him, and he felt weak spurts of magic escape from his penis, cumming from there for the first time. “ah,” he groaned when Father hooked his legs around him, pushing him forward even further, sinking him deeper. “ah!” 

“Come on,” Gaster hissed, seeming frustrated as he pushed and pulled sans until the skeleton finally started thrusting on his own. Tears were already welling in his eyes and Gaster wiped them away, moaning as he felt his son’s small dick move inside him.

Realistically, sans would have been about four inches erect. He did not have the most impressive size, not anywhere close to hitting anything special, but the inappropriateness of it was getting to him. Gaster resumed pushing and pulling sans harder, addicted to the feeling of it barely even touching his walls, being able to control his light son like this. The slight stimulation it provided barely scratched his itch to be filled, but nevertheless he felt himself growing closer as sans openly started crying, gasping nonsensical words, probably trying to ask to stop. “Come on, baby boy, I know you must be so pent up.” It took sans shaking his head to make Gaster groan, an unsatisfying orgasm rolling over him, continuing for a few seconds as he continued to drag sans’ wet dick inside of him. At first he assumed all the slick was from him, but when he finally let sans collapse back, his penis popped out without a noise, and a small amount of cum slid out of him. 

“Oh, wow!” Gaster cheered, as if sans had brought back a drawing from kindergarten, not cumming inside of his Father. “You finally came!” 

At his words sans’ face twisted briefly, Gater only getting a peek of it before it was hidden against the couch, his penis twitching once before disappearing. Pretending not to notice his son crying, the scientist stood up and stretched, gathering all of their discarded clothing around the room. “You should go join your brother in the bath,” he said, pausing before stepping out of the room. “I’m sure he’d like to play with you.”

Slipping into the hall, Gaster waited for a moment before he heard sans get up, padding the opposite direction to the bathroom. Laughing in disbelief at how far he had gotten tonight, Gaster threw the clothes back on the floor in his room, keeping Papyrus’ pants for himself. He quickly fumbled around his nightstand drawer for a minute before drawing out a dildo, practically throwing himself on his bed. Sticking his face in the crotch of his youngest son’s pants, he inhaled deeply, groaning as he sunk the toy inside himself at the same time the scent hit him. Not only could he smell Papyrus’ arousal, he could also smell a hint on sans’ musk as well.

Gaster set a quick pace, slamming the toy into himself over and over as he thought about his boys naked in the bath.


End file.
